Thesis (Ph. D.)--Lehigh University, 2006. / Includes vita. Includes bibliographical references (leaves 675-691).

No / This paper summarises the data from 1819 tests on concrete-filled steel tube columns and compares their failure load with the prediction of Eurocode 4. The full data is given on the website http://web.ukonline.co.uk/asccs2 . The comparison with Eurocode 4 is discussed and shows that Eurocode 4 can be used with confidence and generally gives good agreement with test results, the average Test/EC4 ratio for all tests being 1.11. The Eurocode 4 limitations on concrete strength could be safely extended to concrete with a cylinder strength of 75 N/mm2 for circular sections and 60 N/mm2 for rectangular sections.

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No / This paper presents the buckling behaviour and design of axially loaded concrete filled steel elliptical hollow sections. The experimental investigation was conducted using normal and high strength concrete of 30, 60 and 100 MPa. The current study includes both the stub and slender column tests. Based on the existing design guidance in Eurocode 4 for composite columns, the proposed design equations were found to provide an accurate and consistent prediction of the cross section and buckling capacity of the composite concrete filled steel elliptical hollow sections in axial compression.

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<p>Welded built-up structural steel members are widely used as columns, beams, and beam-columns in various buildings, bridges, industrial complexes, etc. Modern cutting techniques are used in the fabrication of such members. Besides traditional saw cutting and oxy-flame cutting, the modern cutting techniques include plasma cutting, laser cutting, water- jet cutting, etc. The different cutting techniques induce different degrees of Heat Affected Zones (HAZ), which subsequently creates different degrees of geometrical and mechanical imperfections (residual stresses). Therefore, it could be expected that the true behavior of structural steel columns manufactured by such cutting techniques be different.</p><p>The main objective of this investigation was to study the characteristics and behavior of plasma cut-welded H-shaped steel columns at different slenderness ratios. However, this investigation also considered similar flame cut-welded H-shaped steel columns for comparison purposes. The H-shaped column sections were fabricated from plates having specified yield strength of 350MPa. First, the initial plate was cut into plate strips and then the plate strips (flanges and web) were welded together to form the H-shaped section in this investigation. The strength of these columns were established under uni-axial compressive loading with pinned end condition, allowing for minor axis rotation. Moreover, the structural imperfections such as residual stresses and geometrical imperfections were established. The residual stresses distributions were established at various stages of fabrication processes using the "method of section" technique. That is, the residual stresses in initial plate, plate strips (cutting effects), and column sections (cutting and welding effects) were established. Similarly, the geometrical imperfections were established at various stages of fabrication processes in this investigation.The temperature profiles were measured during the cutting and welding processes. As part of the scientific documentation, the mechanical characteristic of virgin steel plates were obtained by standard coupon tensile test.</p><p>Based on the experimental results on column strength, the general behavior of plasma cut columns and flame cut columns were similar. However, it was found that the plasma cut-welded steel columns seemed to carry higher loads than that of flame cut-welded columns for higher slenderness ratios( λ≥1). For lower slenderness ratios (0.5<λ<1), it was found that the flame cut-welded columns had higher strength than plasma cut-welded columns in this investigation. The residual stress distribution of both plasma cut column section and flame cut column section had the same general distribution. However, in general, the flame cut columns had high intensity of tensile residual stresses at their flange tips than the plasma cut columns. Moreover, the out-of-plane imperfections of column sections were within the code limitations. However, it was found that the flame cut-welded H-shaped steel columns seemed to have higher out-of-plane imperfections than the similar plasma cut-welded H-shaped steel columns in this investigation.</p> / Thesis / Master of Applied Science (MASc)

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No / Concrete filled steel columns have been used widely in structures throughout the world in recent years especially in Australia and the Far East. This increase in use is due to the significant advantages that concrete filled steel columns offer in comparison to more traditional construction methods. Composite columns consist of a combination of concrete and steel and make use of these constituent material's best properties. The use of composite columns can result in significant savings in column size, which ultimately can lead to significant economic savings. This reduction in column size can provide substantial benefits where floor space is at a premium such as in car parks and office blocks. The use of stainless steel column filled with concrete is new and innovative, not only provides the advantage mentioned above, but also durability associated with the stainless steel material. This paper concentrates on the axial capacity of the concrete filled stainless steel columns. A series of tests was performed to consider the behaviour of short composite stainless steel columns under axial compressive loading, covering austenitic stainless steels square hollow sections filled with normal and high strength concrete. Comparisons between Eurocode 4, ACI-318 and the Australian Standards with the findings of this research were made and comment.

Shallow embedded steel column connections are widely used in steel buildings; however, there is insufficient research about this connection type to understand the actual rotational stiffness that the connection provides. Shallow embedded steel columns are when a steel column is anchored to the foundation slab and then unreinforced concrete is poured around the base plate and the base of the column. This thesis seeks to further quantify the rotational stiffness available in this type of connection due to the added concrete and improve an existing model in order to represent the rotational stiffness. Existing data from two series of experiments on shallow embedded columns were used to validate and improve an existing rotational stiffness model. These two data sets were reduced in the same manner so that they could be compared to one another. In addition, the rotational stiffness for each test column was determined so they could be evaluated against the outputs of the model. The existing model was improved by evaluating each parameter in the model: the modulus of subgrade reaction, exposed column length, modulus of concrete for the blockout and the foundation slab, flange effective width, embedment depth, and effective column depth. It was determined that the model was sensitive to the subgrade reaction, modulus of concrete, embedment depth and effective column depth. The exposed length was not a highly sensitive parameter to the model. Flange effective width was determined to not be needed, especially when the other parameters were altered.